遇到一个麻烦租客，求帮助。

Phase 1 (Sending Notice): I have one condo in Palo Alto for renting. This January, I plan to sell the condo and gave my tenant 90-day notice to terminate the month-to-month lease. He acknowledged my notice. Later he asked a 15-days extension and I approved.
Phase 2 (Tenant move out): On May 10, 2025, we did final walkthrough and returned my tenant security deposit and my tenant moved out. After that, he keeps quiet until his last property (car) has moved out the garage on June 13, 2025.
Phase 3 (Tenant claim relocation compensation): After his last property moved out, on June 14,2025, he claimed that I should compensate him $28500 for all the costs of moving, storage, disruption of his life. Last weekend, he reduced the amount to $18800, otherwise he may goto court. I am a bit surprised that if he is expecting such high compensation and suggests him to inform me around the time when 90-day termination notification is received so that I have a chance to consider whether to keep the property.

This month, he mentioned he is 90 years old which I don't learn of that as I don't ask him anything about age before and treat him as a regular tenant. During the last three years renting, we have a good relationship. Several times, maybe 5-7 times, on the last day of grace period, he always asks for extension of grace period and I approved.
In my opinion, I made the following mistakes:
Phase 1: I didn't mention the relocation compensation in the termination notice as I didn't realize that this is needed
Phase 2: I should write an note that all the financial payment and due between us are cleared when he move out.
I am glad to compensate him for the relocation cost. However, I am feeling that it costs me too much for the two mistakes I made above.
Question:

• Should I reject his ask for $18800 and go to a court?
• What's the estimated lawyer cost if going to court?
• What's the correct way to terminate a month-to-month lease in Palo Alto (no rent control) if I plan to sell the property. When you terminate month-to-month lease in CA and follow the regulation, normally how much compensation you will give your tenant?